Palu: The death toll from a powerful earthquake and tsunami in Indonesia leapt to 832 on Sunday, as stunned people on the stricken island of Sulawesi struggled to find food and water and looting spread.

The new toll announced by the national disaster agency was almost double the previous figure. Indonesian vice-president Jusuf Kalla said the final number of dead could be in the "thousands."

The damage following earthquakes and a tsunami in Palu. AP

"It feels very tense," said 35-year-old mother Risa Kusuma, comforting her feverish baby boy at an evacuation centre in the gutted coastal city of Palu. "Every minute an ambulance brings in bodies. Clean water is scarce. The mini markets are looted everywhere."

Indonesia’s Metro TV on Sunday broadcast footage from a coastal community in Donggala, close to the epicentre of the quake, where some waterfront homes appeared crushed but a resident said most people fled to higher ground after the quake struck. "When it shook really hard, we all ran up into the hills," a man identified as Iswan told Metro TV.

In Palu city on Sunday, aid was trickling in, the Indonesian military had been deployed and search-and-rescue workers were doggedly combing the rubble for survivors - looking for as many as 150 people at one upscale hotel alone.

"We managed to pull out a woman alive from the Hotel Roa-Roa last night," Muhammad Syaugi, head of the national search and rescue agency, told AFP. "We even heard people calling for help there. What we now desperately need is heavy machinery to clear the rubble. I have my staff on the ground, but it's impossible just to rely on their strength alone to clear this."

There were also concerns over the whereabouts of hundreds of people who had been preparing for a beach festival when the 7.5-magnitude quake struck on Friday, sparking a tsunami that ripped apart the city's coastline.

A Facebook page was created by worried relatives who posted pictures of still-missing family members in the hopes of finding them alive. Amid the levelled trees, overturned cars, concertinaed homes and flotsam tossed up to 50 metres inland, survivors and rescuers struggled to come to grips with the scale of the disaster.

Indonesian president Joko Widodo was expected to travel to the region to see the devastation for himself on Sunday.

C-130 military transport aircraft with relief supplies managed to land at the main airport in Palu, which re-opened to humanitarian flights and limited commercial flights, but only to pilots able to land by sight alone.

Satellite imagery provided by regional relief teams showed the severe damage at some of the area's major sea ports, with large ships tossed on land, quays and bridges trashed and shipping containers thrown around.

Hospitals were overwhelmed by the influx of those injured, with many people being treated in the open air. There were widespread power blackouts.

"We all panicked and ran out of the house" when the quake hit, said Anser Bachmid, a 39-year-old Palu resident. "People here need aid -- food, drink, clean water."

'I just ran'

Dramatic video footage captured from the top floor of a parking ramp in Palu, nearly 80 kilometres (50 miles) from the quake's epicentre, showed waves bring down several buildings and inundate a large mosque.

"I just ran when I saw the waves hitting homes on the coastline," said Palu resident Rusidanto, who like many Indonesians goes by one name.

About 17,000 people had been evacuated, the disaster agency said.

"This was a terrifying double disaster," said Jan Gelfand, a Jakarta-based official at the International Federation of Red Cross and Red Crescent Societies.

"The Indonesian Red Cross is racing to help survivors but we don't know what they'll find there."

The massive tremors were felt hundreds of kilometres away and there has been little word about casualties in Donggala, a region north of Palu where at least one person was reported dead in Friday's quakes.

"We have heard nothing from Donggala and this is extremely worrying," Gelfand said.

"There are more than 300,000 people living there. This is already a tragedy, but it could get much worse."

Pictures supplied by the disaster agency showed a badly damaged shopping mall in Palu where at least one floor had caved in.

Video footage showed a double-arched yellow bridge had collapsed with its two metal arches twisted as cars bobbed in the water below.

An AFP reporter on the scene saw widespread damage some 50 metres inland.

A key access road had been badly damaged and was partially blocked by landslides, the disaster agency said.

Neighbouring Malaysia has offered to send help to Sulawesi, a government spokesman there told AFP, adding Malaysia "was waiting for Indonesia's reply."

Evening prayers

Friday's tremor was also felt in the far south of the island in its largest city Makassar and on neighbouring Kalimantan, Indonesia's portion of Borneo island.

The initial quake struck as evening prayers were about to begin in the world's biggest Muslim majority country on the holiest day of the week, when mosques are especially busy.

Indonesia is one of the most disaster-prone nations on earth.

It lies on the Pacific "Ring of Fire", where tectonic plates collide and many of the world's volcanic eruptions and earthquakes occur.

Earlier this year, a series of powerful quakes hit Lombok, killing more than 550 people on the holiday island and neighbouring Sumbawa.

Indonesia has been hit by a string of other deadly quakes including a devastating 9.1 magnitude tremor that struck off the coast of Sumatra in December 2004.

That Boxing Day quake triggered a tsunami that killed 220,000 throughout the region, including 168,000 in Indonesia.